This invention relates generally to the field of pulmonary drug delivery, and in particular to the aerosolizing of liquid medicament into fine liquid droplets for inhalation.
In the fields of drug delivery and pulmonary therapy, the aerosolization of drugs and other medicaments for pulmonary delivery can provide significant therapeutic benefits. To realize those benefits, there have arisen a variety of atomizers and nebulizers, which can vary significantly in methods of operation. For instance, some aerosol generators operate by vibrating at a relatively high frequency an aperture plate in contact with the material to be aerosolized. By way of example, U.S. Pat. Nos. 5,164,740; 5,586,550; 5,758,637; and 6,235,177, the complete disclosures of which are herein incorporated by reference for all purposes, describe exemplary devices for producing fine liquid droplets in such a fashion. Such devices have proven to be tremendously successful in aerosolizing liquids. Another technique for aerosolizing liquids is described in U.S. Pat. No. 5,261,601, also incorporated herein by reference for all purposes, and utilizes a perforate membrane disposed over a chamber. The perforate membrane comprises an electroformed metal sheet using a “photographic process” that produces apertures with a cylindrical exit opening.
Commonly, such aerosol generators operate by using a vibratory element to drive an aerosolizing element (e.g., aperture plate, membrane, etc.). In many cases, the vibratory element comprises a piezoelectric and/or piezomagnetic material such as one of many ceramics known in the art to exhibit such properties. When excited by the appropriate field, the piezo will expand/contract, such that application of an oscillating field can produce oscillating vibration of the piezo (and, by extension, the aerosolizing element) at a frequency related to that of the oscillating field. Often, the field will be applied to the piezo through one or more electrodes in electrical communication with the piezo.
In use, aerosol generators can be subjected to a variety of environmental conditions, many of which can threaten to degrade the performance of the generator; for instance, during operation, the piezo and/or the electrodes may be in danger of exposure to the fluid being aerosolized. Those skilled in the art will recognize that, in many cases, prolonged exposure to such fluids can result in corrosion of the piezo and/or the electrodes, and even relatively brief exposure can vitiate the electrical communication between the piezo and the circuitry by which it is driven (for example, by short-circuiting the electrodes and/or otherwise interfering with the electrical communication between the electrodes and the piezo).
Likewise, various cleaning procedures can prove harmful to the operation of the aerosol generator if care is not taken. For instance, in many cases aerosol generators are used in hospitals and/or other institutional settings, where strict sanitization policies often are enforced to prevent cross-infection by multiple users of a generator. Merely by way of example, aerosol generators may be exposed to potentially corrosive substances, such as solvents and disinfectants. In addition, generators may be exposed to relatively high levels of heat, pressure, and/or humidity during sanitization processes, such as autoclaving and the like. Without protection, therefore, the relatively sensitive components of aerosol generators (including, for example, their piezos and/or electrodes) may be damaged during sanitization and/or the operational lives of such components may be limited significantly by repeated sanitization procedures.